Pathogenicity

• Mucous membranes
• Respiratory tract
• Gastrointestinal tract
• Genitourinary tract
• Conjuctiva
• Skin
• Parenteral route

the same as the portals of entry

• Via cut or scratch
• Via vector (flea, mosquito, ect.)
• Through hair follicles or sweat -glands

• Uptake by epithelial cells
• Uptake by APC's

skin

• 1. Adherence 
•      • Adhesions allow microbes to bind to specific cell types

2. Infection; growth of microbe

• 3. Damage to host
•      •Invasion of tissues 
•      •Toxins

• Hiding within host cell
• Evasion of complement
• Evasion of phagocytosis
• Exoenzymes
• Avoiding antibodies
• Antigenic variation

• C5a peptidase
• Cytolytic toxins

• Capsules
• M protein
• Fc receptors

• Escape from the phagosome
• Prevent phagolysosome fusion
• Survive within the phagosome

• Protein A on the antigen
• Fc portion of igG is not available for receptor

•Coagulase – clots fibrinogen in the blood

• •Kinases – digest clots to allow spread of
• microbe. Ex: streptokinase

•Collagenase – breaks down collagen

•Using host’s nutrients

•Direct damage by invasion

•Producing toxins

•Inducing hypersensitivity reactions

• gram positive bacteria
• Secreted by living bacteria
• Usually a protein
• Can vaccinate using toxoids

Released by dying bacteria and can occur in any gram negative bacteria

Derived from LPS from Gram negative cell wall

1.A-B toxins

2.Membrane-damaging toxins

3.Superantigens

4.Other exotoxins

Lethal Dose for 50% exposed

• A measurement to compare potency of
• different toxins

–LD50 for Botulinum toxin = 0.03 ng/kg

–LD50 for Staphylococcal enterotoxin = 1350 ng/kg

Have 2 protein parts: A and B

B – binds host cell

A – has toxin function

damage nervous system

Ex:  Botulinum toxin

cause intestinal symptoms

Ex:  Cholera toxin

lyse cell or interfere with cell function

Ex:  Diphtheria toxin

Disrupt plasma membranes. results in host cell lysis

•Pore-formation

•Phospholipases

Streptococcus pyogenes - streptolysin O –  

Staphyloccus aureus - beta-hemolysin

Clostridium perfringins – causes gas gangrene

Bind T cell receptors. triggers massive cytokine release

Non-specific, mass-activation of T cells

Staphylococcus - toxic shock syndrome

•LPS - lipopolysaccharide-

–Active portion – Lipid A

•Source of endotoxin – Gram negative bacteria (OM)

Cell lysis

–Bacteria die

–Bacteria killed by the immune system

–Bacteria killed by antibiotics

Damage associated with inflammation

Macrophages --> release cytokines --> fever & inflammation

B cells --> non-specific activation

worsen the effects of endotoxin

endotoxin in large amounts triggers systemic inflammation & blood clotting proteins

Disseminated intravascular clotting - a disorder in which there is an over activation of blood clotting in the blood vessels and resultant bleeding within the body

Allow for spread of infection

•Bodily Secretions

    –Mucous; sneezing & coughing

    –Feces

    –Semen & vaginal secretions

•Blood

•Skin shedding

•Organize it

• •Want to be able to run as few tests
• possible in order to quickly identify organisms

•All of the information is used to create: Dichotomous Keys